The present invention relates to a buffer device for use with the seats of vehicles and, more particularly, it relates to a buffer device for use with the seats of vehicles such as a car, forklift truck and tractor and provided with a parallel linkage mechanism.
When vehicles run on a rough road, upward and downward vibrations, shock and the like act on drivers and other persons in the vehicles. As a measure to prevent this, there has been well-known a buffer device wherein a parallel or X-type linkage mechanism is arranged between a seat and the floor and combined with buffer members and shock absorbers to buffer the shock and reduce vibrations.
In the case of the buffer device wherein the parallel linkage mechanism is employed, front and rear links are located parallel to each other between the seat and a floor bracket to hold the seat float from the floor bracket.
The response of the seat relative to such inertial force as shock and vibrations becomes better as the slope of the linkage mechanism becomes closer to horizontal in relation to a horizontal face made by the links.
The same thing can be said in the case of using the X-type linkage mechanism, but it is structually impossible in this case to bring the links to a horizontal state. Therefore, the use of the parallel linkage mechanism is more practical when the response of the seat relative to the inertial force is aimed at as a target.
As the front and rear links become more and more horizontal, however, the rotating path of the seat becomes accorded with that of each of the links, and one of the links sometimes moves under the horizontal line. The seat is rotated and inclined forward or backward in this case, thereby causing the possibility of bringing the person, who is seated on the seat, into danger.